Determining the ratio of transformers
As a relative newcomer to this site I apologize if this tip has been posted before
To determine the ratio of an output transformer, inter-stage transformer or indeed practically any transformer, simply feed 1 volt AC into the secondary and the measure the voltage across the primary. This gives the ratio. Where do I get 1 volt AC I hear you cry? One can simply add a few turns to an old mains transformer. Choose one where there is a gap between the laminations and the outside of the windings, this avoids the need to dismantle the transformer Around 8 turns is a good starting point, adjusting the number of turns until 1 volt is obtained. If you have a transformer with 4v and 5v secondaries they can be wired is series opposition to give 1 volt. Elstone made mains transformers with 0-4-5-6.3v as well as ht windings for universal replacement purposes. The foregoing only applies to mains and audio transformers of course not high frequency types, switch mode etc.
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